Abstract
Natural rubber (NR)/hexagonal mesoporous silica (HMS) nanocomposites (NRHMS) with enhanced thermal and hydrophobic properties were facilely prepared via in situ sol–gel formation with pH adjustment using a low sulphuric acid (H2SO4) acid concentration. The effect of the amount of 0.5 M H2SO4 (2.5–10 g) added into the pre-synthesis mixture on the physicochemical properties of the obtained NRHMS nanocomposites was investigated. With a small addition of H2SO4 solution, the fabricated NRHMS nanocomposite possessed an improved wormhole-like mesostructure arrangement with a thicker silica wall, which retarded the thermal decomposition of the NR phase, as deduced from the auto-oxidation of NR by thermogravimetric analysis. The H2O adsorption–desorption measurement revealed an increased hydrophobicity of the NRHMS composites, explained by the acid-catalyzed bridging of free silanol groups to siloxane bonds, which was supported by the X-ray photoelectron spectroscopy analysis. Scanning transmission electron microscopy with energy dispersive X-ray spectroscopy elemental mapping revealed a good dispersion of the NR phase within the mesostructured silica. However, a high amount of added H2SO4 solution led to silica–NR phase separation due to the decreased hydrophobic interaction between the silica precursor and rubber chain, as well as an agglomeration of the NR phase itself. The mechanism of NRHMS nanocomposite formation under pH-controlled conditions was proposed to proceed via a cooperative self-assembly route.
Highlights
In the past few decades, the soft template-based synthesis method has been utilized to prepare a variety of mesoporous-structured materials [1]
The preparation of mesoporous silica based-polymer nanocomposites has been broadly summarized into the four methods of (i) blending, a direct mixing of polymer and mesoporous silica by melt or solution blending [19, 20], (ii) in situ polymerization, a dispersion of the surface-modified silica phase in monomers followed by polymerization [21, 22], (iii) surface-initiated polymerization, a grafting of polymeric moieties onto mesoporous silica via covalent interaction [23, 24], and (iv) in situ sol–gel formation, a direct preparation by either impregnation of polymeric molecules into the silica framework [25] or fabrication of a mesoporous silica/polymer nanocomposite via softtemplated self-assembly [26]
We explored a simple approach for fabricating Natural rubber/hexagonal mesoporous silica (NRHMS) nanocomposites with enhanced thermal stability and hydrophobicity based on pH adjustment using a mild sulfuric acid solution (0.5 M H2SO4)
Summary
In the past few decades, the soft template-based synthesis method has been utilized to prepare a variety of mesoporous-structured materials [1]. The choice of HMS reflects its exceptional physicochemical properties compared to conventional periodic mesoporous silica, Modification of HMS surface properties, both chemically and physically, has been widely investigated for preparing unique materials that are suitable for various specific purposes. Modified HMS materials provide a low water affinity on the surface while still possessing its distinctive properties, and so exhibit a good performance in the adsorption of N-nitrosamines from tobacco extract solution [16] and controlled release of poorly water-soluble drugs [17]. Physical modification of HMS with organic polymers is an interesting method to increase its hydrophobicity due to its relatively easy approach and low cost, and that it provides further possible functionalization of both the silica and organic phases. The preparation of mesoporous silica based-polymer nanocomposites has been broadly summarized into the four methods of (i) blending, a direct mixing of polymer and mesoporous silica by melt or solution blending [19, 20], (ii) in situ polymerization, a dispersion of the surface-modified silica phase in monomers followed by polymerization [21, 22], (iii) surface-initiated polymerization, a grafting of polymeric moieties onto mesoporous silica via covalent interaction [23, 24], and (iv) in situ sol–gel formation, a direct preparation by either impregnation of polymeric molecules into the silica framework [25] or fabrication of a mesoporous silica/polymer nanocomposite via softtemplated self-assembly [26]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
